Obtain the JSON Key:
Create a service account in your Google Cloud project.
Download the JSON key file for the service account from the Google Cloud Console. (https://cloud.google.com/iam/docs/service-accounts-create)

Configure the Plugin:

In your Bubble app, add the "GOOGLE JWT" plugin to your project.
In the plugin settings, provide the JSON key you obtained from the Google Cloud Console.

The action will give an access token as response